In radio communications networks of today the number of radio base stations is increasing as well as the number of cells. It is important to detect a malfunction in a cell of the radio base station in order to provide a reliable radio communications network with available communications possibilities. There exist a number of different fault detection systems in radio base stations of today. Such fault detection systems comprise sensors, software triggered observability functions and similar devices that generate an alarm when malfunction is detected and an operator or similar is informed about the alarm. Thus, the operator is made aware of the malfunction.
However, the radio base stations of today comprise a numerous of components and software in which malfunctions might not be detected by installed monitoring equipment and thus some malfunctions may not be detected. For example, when cells no longer carries any traffic, when no incoming handovers are detected or when no new attached user equipments are allowed are examples that may occur when there are no active user equipments in the cell or when a faulty state of the cell. A faulty state means that the cell suffers from an abnormal state or condition and is often referred to as a Sleeping Cell.
A number of solutions have been discussed whereby a sleeping cell may be efficiently detected.
In one proposed solution, a traffic history of traffic statistics in the cell is kept in each radio base station of the network e.g. for one week. When current traffic statistics shows a low activity in the cell, a comparison is made against the traffic history to see if the low activity is “normal” or not. The problem with such a solution is that it is very hard to implement an algorithm that can learn at the same time as it can detect faulty situations.
In another proposed solution, a number of “self-tests” are performed, i.e. when the traffic statistics show low activity in the cell, a number of tests are performed. One test would be to awake user equipments in Idle Mode and ask the user equipments to contact the network, i.e. the radio base station, via a random access channel. A problem with the self-test solution is that the test procedures that have been proposed so far have been questioned from a number of angles, e.g. interoperability with user equipments, robustness, accessibility downgrading etc.